1. A Global 86 GHz VLBI Survey of Compact Radio Sources Sang-Sung Lee MPIfR In collaboration with A.P. Lobanov, T.P. Krichbaum, A. Witzel, J.A. Zensus (MPIfR, Bonn) M. Bremer, A. Greve, M. Grewing (IRAM, Grenoble) 26.09.2006 8 th EVN Symposium, Torun, Poland

2. Outline  Introduction - mm VLBI, Previous Surveys  Results - Images  Brightness temperature (T B ) and jet physics - T B distribution, T B vs. Apparent jet speed, T B along the jets  Summary

3. Outline  Introduction - mm VLBI, Previous Surveys  Observation - Source selection, Calibration  Results - Images  Brightness temperature (T B ) and jet physics - T B – Apparent jet speed, T B along the jets  Summary

4. Millimeter VLBI IntroductionResultsTb and Jet physicsSummary 1.VLBI experiments at mm wavelengths (e.g. 43GHz, 86GHz, 150GHz, 230GHz) 2.A unique tool for exploring the physics of compact radio sources with about 6 times better resolution (40 micro-arcsec at 86 GHz) than space-VLBI at 6 cm wavelength 3.At mm wavelengths, synchrotron radiation becomes optically thin, so mm-VLBI makes it possible to look deeper in the “VLBI core”, invisible at cm wavelengths 1983 First VLBI fringe detection at 89GHz Readhead et al. 1983 1995 CMVA (86GHz) (The C oordinated M M V LBI A rray) 2004 GMVA (86 GHz) (The G lobal M M- V LBI A rray) present Haystack + (Ef, On, Pv, Pb, Mh) + VLBA ( 8x25m) VLBA (8x25m) + (Ef, On,Pv,Pb,Mh) GMVA web - http://www.mpifr-bonn.mpg.de/div/vlbi/globalmm/

5. Previous surveys IntroductionResultsTb and Jet physicsSummary VLBI Surveys at 86 GHz 1.Beasley et al. (1996) 2.Lonsdale et al. (1998) 3.Rantakyro et al. (1998) 4.Lobanov et al. (2000) 5.This survey - 3~4 times better sensitivity - larger sample (127sources) taken from surveys at lower freq. - 121(95%) were detected and 109 imaged This Survey

6. Source selection IntroductionObservationResultsTb and Jet physicsSummary References of source selection 1. The VLBI samples: - 22 GHz (Moellenbrock et al. 1996) - 15 GHz (Kellermann et al. 1998) 2. The multi-frequency monitoring data: - Metsahovi at 22, 37, and 86 GHz (Terasranta et al. 1998) - Pico Veleta at 90, 150, and 230 GHz (Ungerechts, priv. comm). Flux density > 0.3 Jy at 86 GHz Declination > - 40 degree Excluded some bright sources imaged at 3mm before Survey Observations with Global 3mm VLBI Three sessions: Oct. 01, Apr. 02 and Oct.02 3~4 scans of 7-min dur. per a source Antennas : 8 VLBA + 5 European Ant. Max. baseline sensitivity ~ 0.1 Jy Image sensitivity < 10 mJy/beam Bandwidth: 64 or 128 MHz Sampling : 1-bit or 2-bit Correlation : Mark IV at MPIfR Bonn Sky distribution of the sources RA [hrs] Dec [Degrees] 0 4 8 12 16 20 24 90 60 30 0 -30 -60 -90

7. Calibration IntroductionObservationResultsTb and Jet physicsSummary Correlation CalibrationImaging FOURFIT MK4IN Amp. calibration FRING MAPPLOT CLEAN Fringe detection : FOURFIT with subsequently narrowing the search window Amplitude Calibration : Tsys measurements, Gain curves,opacity correction and amplitude self-calibration Phase Calibration : manual phase-calibration and self-calibration Imaging : t avg = 30 sec, natural weighting, no uv-tapering, beam size = 0.05 x 0.36 mas Correlator at MPIfR Software (Alef et al. 1998) AIPS DIFMAP (Shepherd et al. 1994)

8. Images IntroductionResultsTb and Jet physicsSummary Lee et al. 2006 in prep

9. Brightness Temperature (T B ) IntroductionResultsTb and Jet physicsSummary And if, then the lower limit of T B is obtained with d = d min. (e.g. SNR = 6.5; Beam ( a x b ) = ( 0.1 x 0.07 mas) => d min = 0.035mas) (A.P. Lobanov 2005)

10. T B distribution IntroductionResultsTb and Jet physicsSummary (Lobanov et al. 2000) VLBI coresJet components (Lee et al. 2006, in prep.) VLBI cores Jet components

11. T B vs. Apparent jet speed IntroductionResultsTb and Jet physicsSummary T B,core vs. Jet speed (N=86) Apparent Jet speeds from 2cm survey (Kellermann et al. 1998) T B,jet vs. Jet speed (N=39) Red triangles are lower limits of T B

12. Evolution of T B along the jets IntroductionResultsTb and Jet physicsSummary NRAO 140 3C 454.3 OJ 287 NRAO 190 Red circles are the predicted T B in shocks with adiabatic losses dominating the radio emission. Blue circles are the observed T B. (Lee et al. 2006 in prep.) Assumptions are made like the following: (Lobanov et al. 2000)

13. Summary IntroductionResultsTb and Jet physicsSummary 1.We conducted a large global 86 GHz VLBI survey of compact radio sources, using a global 3mm VLBI array. 2.The survey is the largest and most sensitive one (rms Image < 10 mJy/beam) 3.It provides a detection rate of 95% out of 127 sources and a total set of images of 109 sources. 4.We estimated brightness temperatures (T B ) of the cores and secondary jet components from the measurements of flux densities and sizes of the components, taking into account resolution limits of the data. 5.The T B of the cores are higher than those of the secondary jet components and seem to be correlated with apparent jet speeds rather than those of the secondary jet components.